The common practice in forming fibers of mineral materials, such as glass fibers, is to pass the material in a molten state to the orifices of the peripheral wall of a centrifuge or spinner to create primary fibers. Thereafter, the primary fibers are further attenuated into secondary fibers of smaller diameter by the action of a flow of gases discharged downwardly from an external annular blower. Some fiber forming processes, such as the Supertel process, use a high velocity gaseous burner for the secondary attenuation of the mineral fibers. Other fiberizing processes, such as low energy processes, use blowers only for turning the mineral fibers into a downwardly moving cylindrical veil, rather than for attenuation.
The manner of supplying molten glass to the spinner peripheral wall for fiberization varies. One method uses a distributor or slinger cup mounted for rotation radially inwardly of the spinner peripheral wall. A single stream of molten glass is supplied to the slinger cup, and the slinger cup distributes the molten glass as a multiplicity of coarse streams which are thrown by centrifugal force to the spinner peripheral wall. In such a process the spinner bottom wall serves little function, and is generally provided with a large opening or central bore.
In another process for supplying molten glass to the spinner, a single stream of molten glass is supplied to the spinner bottom wall, and the molten glass flows by centrifugal force to the spinner peripheral wall. In such a method of molten glass distribution, the spinner bottom wall is an essential element in the distribution process.
In order to improve mineral fiberization processes, it has become desirable to stabilize the veil of mineral fibers produced from the spinners. As the throughput from fiberizers is increased, and as the diameter of the spinners is increased, it becomes increasingly important to stabilize the veil of mineral fibers. The veil of mineral fibers has a tendency to "dance" or wobble in an unstable manner, and this adversely affects the distribution of mineral fibers into the insulation products being formed.
Another problem in mineral fiberization is that the veils have a tendency to collapse or neck down to a smaller diameter. This causes greater fiber entanglement and presents problems in evenly distributing the fibers into a thermally efficient insulation product. An improved system is needed to prevent the veils from collapsing.
One means for providing veil stabilization is the use of a cone attached to the spinner bottom wall. Another attempt in the past to stabilize the veil is the use of air introduced via a small conduit threaded down through the hollow quill of the spinner. These efforts to stabilize veils of mineral fibers have been only partially successful. An improved method for stabilizing the veil is needed.